1. Field of the Invention
The present invention relates to a glass antenna device for a vehicle, in more particular, to a glass antenna device for a vehicle having stable operating characteristics.
2. Related Art
A glass antenna device for a vehicle, in which an antenna element is installed on a window glass of a vehicle, has been conventionally known. For example, Japanese Patent Laid-Open No. 2005-109811 and Japanese Patent Laid-Open No. 2007-36446 disclose conventional glass antennas for a vehicle.
Further, in the glass antenna device for a vehicle in which the antenna element is installed on the window glass of the vehicle, it has been known to form the antenna element by conductor lines disposed in a lattice shape in order to improve invisibility and perceptibility of the antenna element on the window glass. For example, Japanese Patent Laid-Open No. 2005-142984 discloses such a kind of the glass antenna device for a vehicle.
The glass antenna device for a vehicle is mainly installed in a vicinity of a boundary between the window glass and a body frame, that is in general a corner of the window glass, since the glass antenna device for a vehicle is requested that a field of view of an operator or a crew will not be disturbed. On the other hand, the glass antenna device for a vehicle is demanded to have the stable operating characteristics without being affected by electrical influences due to outside members such as the body frame.